They would make sure it gets lots of water and it needs sunlight to so some kind of source that could replace the sun
Group 2, or in the Alkaline Earth Metals section. This is due to the necessity to have a +2 charge to balance out or negate the -2 charge two Bromines carry.
The gas will obey Boyles Law:
P1 V1 = P2 V2 where P1 and V1 are the original pressure and volume and P2 and V2 are the new values.
If V2 = 2V1 (given) then:
P1 V1 = P2 *2 V1
P2 = P1 V1 / 2V1
P2 = P1 / 2
In other words the pressure is halved. (answer).
